Have I been missing this obviously simple module all this time, and if so, what is it called? (If not, then watch this space for a new module announcement.)

Oops, sorry. I skipped over the "watch this space" part when I read this thread, and went off to write the module (since I've wanted this many times too.) It's now uploaded to CPAN as IPC::Run::Simple. If you want to take it over, let me know.